The invention relates to an adaptive filter comprising a delay circuit, taps of which are connected to amplitude control circuits, a difference-determining circuit for forming an error signal between a signal which is corrected by the filter and a reference signal having a waveform which substantially corresponds to a desired waveform for the signal corrected by the filter, circuits for obtaining control signals for the amplitude control circuits being controlled by means of said error signal.
Nachrichten Technische Zeitschrift 1971, volume 1, pages 18-24 discloses an adaptive filter of the above-mentioned type. Such a filter is suitable for use in television receivers if the automatic adjustment of the filter is effected in response to a teletext signal present in the television signal as a data signal in one or more line periods during the vertical picture blanking period and which may be used as a pseudo-random test signal for the filter.